Anesthesia & Analgesia: March 2016
AUTHORS: Sviggum, Hans P. MD et al
BACKGROUND: Intrathecal (IT) morphine is considered the “gold standard” for analgesia after cesarean delivery under spinal anesthesia, most commonly administered at a dose of 100 to 200 [mu]g. There is less experience with IT hydromorphone for postcesarean analgesia and limited information on its optimal analgesic dose. We conducted this study to determine the effective analgesic dose for 90% patients (ED90) of IT hydromorphone that provides effective analgesia for women undergoing elective cesarean delivery and its potency ratio to IT morphine.
METHODS: In this dose-finding trial, 80 patients received spinal anesthesia for cesarean delivery. Participants were randomized to receive IT morphine or IT hydromorphone at a dose determined using up-down sequential allocation with a biased-coin design to determine ED90. All patients received standardized multimodal analgesia postoperatively in addition to IT opioid. An effective dose was defined as a numeric response score for pain of <=3 (scale 0-10) 12 hours after spinal injection.
RESULTS: The ED90 was 75 [mu]g (95% confidence interval [CI], 46-93 [mu]g) for IT hydromorphone and 150 [mu]g (95% CI, 145-185 [mu]g) for IT morphine. At these doses, the 95% CI for the percentage of patients with effective analgesia (numeric rating scale <=3) was 64% to 100% for hydromorphone and 68% to 100% for morphine. Exploratory findings showed that the incidence of nausea and pruritus was not different among the most commonly used doses of IT hydromorphone (P = 0.44 and P = 0.74) or IT morphine (P = 0.67 and P = 0.38, respectively). When administering IT opioids at ED90 doses or higher, 100% (21/21) of IT hydromorphone and 95% (37/39) of IT morphine patients were satisfied with their analgesia.
CONCLUSIONS: The ratio of IT morphine to IT hydromorphone for effective postcesarean analgesia is 2:1. Patient satisfaction was high with both medications.